You should always but a Betta in a breeder net when the intake is off, or any small fish. I never take the intake off though. I just clean it and then do a water change.
See this is why you shouldn't let Betta fish watch Finding Nemo. He's got it in his head that he can stop the impeller and swim back out. But there's no other fish out there with a big stem from a fake plant to save him!
From a distance you cannot even see them, but if you get right up close you can see a few tiny pinpicks that haven't healed yet, but that is it. Most of his "battle wounds" have already healed : )